The biofilm-forming marine bacterium Pseudoalteromonas atlantica expresses phase variation in production of the adhesin extracellular polysaccharide (EPS). Phase variation of EPS production is caused by the precise excision and insertion of IS492, at a target site within the eps locus. IS492, a member of the IS110/IS492 insertion sequence family, encodes for the transposase MooV. MooV belongs to a novel family of DNA recombinases, the Piv/MooV recombinase family, which does not share any of the conserved amino acid motifs found in the other DNA recombinase families. To ascertain if the transposases of the IS110/IS492 Family and Piv, the site-specific DNA recombinase, define a new family of DNA recombinases that share a common mechanism for DNA recombination, I will genetically characterize mechanisms of MooV-mediated IS492 transposition for comparison with Piv-mediated site-specific inversion. I will focus on determining essential proteins and DNA sequences involved in the recombination reaction in vivo. This research will explore a new area within the field of DNA recombination, and contribute to understanding molecular mechanisms of DNA recombination involved in essential cellular functions.